Remote-control system for aircraft



Jan. 1, 1952 p R MURRAY TAL 2,580,453

l REMOTE-'CONTROL SYSTEM FOR AIRCRAF T VMM?" l Jam l, 1952 P. R. MURRAY ETAL REMOTE-CONTROLv SYSTEM FOR AIRCRAFT 4 Sheets-Sheet 2 Filed Oct. 14, 1944 @0A/rim 50x Jac/m57.

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REMOTE-CONTROL SYSTEM FOR IRCRAFT Janl 1952 P. R. MURRAY ETAL 2,580,453

REMOTE-CONTRL SYSTEM FOR AIRCRAFT` .Y

patented Jan. 1,

Peter Murray and Donald c; engin; bams,

as represented by the Secretary' of War Application October 14, 1944 Serial No. 558,708

(o1. 25th-#2)" (Granted under theV act of March 3', 1883; asl

amended April 30, 1928;. 370 0. G. 757) i claims.

The invention described herein may brnanufactored and usedV by orl for theGovernmemnt for governmental purposes; without the payment` to us of any royalty thereon:

This invention relates te-'impro-vementsinwireless remote control systems andmore particularly to improvements in thelmeans for controllingthe remotely positioned equipment.`

A great many attempts have been made to control models of equipment` by wireless means and a mea-sure of success has been attained but the art has lagged-` irrthe-A fulfillment of i completefunctional control of remotely positioned full-l sizef equipment.

Inaccordance with; the present-invention; complete and positive controlofa-ll operational func# tions' has been accomplished and the controlsso` arranged and designed' that they simulateactualoperating conditions;

It is, therefore, aA primeobject of:` thisirivn 20 tion to providea system of controls4 to' perforin any operational function of remotely positionedI equipment'. s

receivingVA the cbritrllhg intelligence 'tlough tli medium of propagated electromagnetic energy.

A further object is to" provide" a safe positive" remote control system' for`V an airplane in fligifit.r

These and' further objects' will' be'oiners'dre 30" app-arent in the followings description as eX-I- piified and uiustrated-in the drawing-sin whi'cni;

Figure I1 is a block diagram of the remote controlltransmitting system; s s s Figure 2V represents a block diagram offther receiving and selecting systemof` theinvention; Y

Figure 3 is a schematicv diagram of a control unit used in combination with ay transmittingunit; and

Figure 4 illustrates `a schematic diagram of a function selector unit including relays and switches used in combinationwith a receiver located in the equipment tobe controlled;

Figure-5 illustratesfadetail of the' circuit of the` modulator of the remote control transmitting system.

Figure 6 illustrates a detail of the circuitof the control loof: of the remote control transmitting-` system.

The system of remote control tobe describedis between a master station, where a controlling radio transmitter is located, and' acontrolled stas tion', which in the embodiment described is lo# of the airplane; The controlled airplane willv bei called` the slavelplane.

In one' embodiment oft the system ot thiss in- Vention, the illustrated block diagram represents i a control box` IIl (Figa 3) detailsof which willbe'! anA airplanetpreparing to takeoiifro'm tl'ieiground` and, inconjunction with` such `flight,` the control ofthe various functions incident thereto;

Theatoremention'edi operation'. consists of selecting the desired operating. functionv by actu-` ating certain switches onl thelsaidJ control.' box I I,

f (Fig. 1),. said switches in turny selecting a1 fixed low frequency fromhthe multifrequency: low fre-` quency modulator I2l (Fig. 1'), said frequency being predetermined" and relatedto the desired operating function.Y The selectedi low frequency is fed into and frequency'` modulates the: transmitter I3 (Fig. l). Thivmodulated carrier ofthe transmitter I3 is propagated into space via the antenna 9. The control signal consists of the several modulating frequencies.

the duration of modulation; in othersthe nature of the control is effected.` by1 thenumber of pulses of modulation, as will behereinaf-ter explained;

The aforem entionedV modulated,v signal' is intercepted bythe antennaf of the receivingi system,`

Figure 2. Radio. frequency? amplifier` IIl. ampli'-A fles the desired signal and rejects the imagefre-` quency to a considerable deg-reel.` The: crystal oscillator and harmonic ampliiier I5 generates a` heterodyne signal-by: amplifying' tlef fourthharmonic" of the. crysta'lio'scillator andA tliehetero` dyne frequency; islselectedr to be" lower than the required signal frequency.. The aforemeiitioned two signalsf are combined in tliel` usual manner in the converter stage ItJ and the' difference frequency amplified by" theY intermediate frequency amplier I7.

The signal is` than fedro thel limiter stage` ItI where any amplitude modulation due to noise` impulses isA removed tov a considerable extent;

Discriminator stagey I'9 converts theY frequency` variationsv of the incoming: signal to audio frequency signals.

The audio frequency thus` recovered; is: then amplied by the first audio amplifier 2,0 and the output of the amplifier 20 is fed, simultaneously,v to the grid of the monitor amplifier' 224 and the selector amplifier 2|. I

For testpurposes a head setiisconnectedin cated lin anfairplaneand whichcontrolsithe flight the output oliV the Ymonitor amplifier 2,2?.

In some cases;

with control means means for transmitting andk 25 me degree 0f' Control exercised'sproportonal to The output of the selector amplier 2i, whose relative value is indicated by an audio frequency meter (not shown), is I'ed to the multi-selector channels B', C', D', E', F', G', H, I', each of which comprises a voltage ampliiier 24, frequency lter 25, rectifier 26 and operating relay 2 l. The component parts are shown only for channel B'. When the desired modulation frequency, as determineo. bythe nature of the operational function selected, is present, the corresponding relay 2 in the selector channel will operate cue to the increased plate current in the rectiiier tube. It is seen that the action of frequency nlter 25, rectii'lei` 26, and operating relay 21 is to isolate a modulating signal of a particular frequency and produce a direct current voltage at output terminal B" ol' channel B', which persists as long as the modulation continues and desists when the modulation ceases. In similar fashion modulations of the other frequencies are isolated in the channels marxed C', F', H', G', I', D', E', and similarly direct current control voltages are produced at terminals C, F", H", G", I", D", E" of receiver receptacle 5t of Fig. 2 whenever the corresponding modulation frequencles are received in receiver 5.

In selector unit 28 (Fig. 4) the control voltages are received on terminals B to I" of selector connector plug 55, which plugs into receiver receptacle 5e. These voltages are distributed by the several switches hereinafter to be described and routed to the several banks of terminals marked "To gyro section of servo 16, To valve section of servo 58, and "Auxiliary functions socket, 12. From these terminals the voltages pass to the actual control mechanisms, which form no part of this invention.

To further clarify the control functions of the invention, reference is had to Figures 3 and 4. Referring more particularly to Figure 3, the control box I i comprises a multiconductor modulator connecting plug 3U which serves to connect the control box II to the multifrequency low-freN quency modulator I2. Aflixed to the control box I l is a male type multiconductor socket 3| which is designed to receive the connector plug 36.

Modulator l2 (Fig. 5) contains its own power supply 15 and a set of audio frequency oscillators each on a separate frequency. One only 13 is shown. Outputs of all the oscillators are collected in a mixer 19 and applied as modulation to a carrier in transmitter I3.

The means for keying the oscillator 'I6 is as follows: The oscillating tube 11 of oscillator 16 has its cathode 18 connected to terminal B of control box II. Following the lead from terminal B it is seen this circuit passes through terminal Reset, through switch 33, through switch 52 (normally closed to terminal Remote) to ground in control box Il, through terminal A to ground in modulator I2 and back to oscillator 16. Thus closing and opening switch 33 controls the oscillation of oscillator 16, and controls the presence or absence of its respective modulation on the carrier in transmitter I3. Similarly applications of the other oscillations to the carrier are controlled by the several other switches in control box II. All circuits have a common ground return through terminal A.

Terminal J Yconnects to power supply 15 in modulator I2 and to switch 32 in control box II, so that switch 32 is the master switch for moddlator I2 turning it on and off.

Power supply for the relays and lamps of control box I I is received from modulator I2 through terminal N. Switches 49 and 1 are ganged toA gether. Thrown in the upward position they adapt the circuit for l2 volt supply, and in the downward position they adapt 1t ior 214 volt supply. Tney are always closed one way or the other.

The types of control exercised by control box II are ol two types. The first type is a pulse type and is controlled by switch 33. Closing switch 33 to terminal Reset causes the transmission of the modulation respective to the oscillator 'l5 connected. This is denominated the "reset signal." As will appear, the resulting control action in selector 25 is to bring the arms 56, 5I and 62 of stepping switches 5l, 53 and 6d to the positions lIluB, lIB and IZIB respectively. This control is positive and is independent of the length of time switch 33 is closed (beyond a certain short minimum) and switches 5s, 59, 56 stay in their positions after the reset signal is discontinued.

If switch 33 be thrown to Step the oscillator associated with terminal C puts the modulation on transmitter I3 which is denominated the "step signal. As will appear the resulting control action is to move the arms 56, 6I and s2 oi stepping switches 51, 59 and 6I), respectively, up one step. These switches move up one step for each closing or" switch 33, and one step only, and remain in position when switch 33 is opened.

In order that the operator at the control box I I may at all times know the positions occupied by step switches 5l', 59 and 66 in selector 26 these switches are duplicated in control box Il by step switches 35, 36 and 31. Switches 36 and 31 would not need to have so many steps or contacts as switch 35, but they are more readily procured as parts of a 3-deck switch having 10 contacts per deck. These three ganged switches are operated by a relay 38 in exactly the same manner .as the ganged switches 51, 59 and 66 are operated by relay 1I. Duplicating control switch 33 and ganged thereto is switch 34. When switch 33 is closed to Reset, switch 34 closes to Reset thereby passing current through the upper coil of relay 38 and pulling the arms 36, 40 and 4I of switches 35, 36 and 31 to reset positions 6A, 86A, 96A respectively. Similarly for each successive closing of switch 33 to Step position, switch 34 likewise closes to Step position and passes current through the lower coil of relay 38 thereby causing the arms 39, 40, 4I to move successively to contacts IA, etc., BIA, etc.. SIA, etc. Between terminals IA, 2A, etc., and ground are placed lights, in bank 48 and current passes from arm 39 through that terminal on which it rests and through the connected lamp. The lamp by lighting indicates the position of arm 39 and also of arms 56, BI and 62 in selector 28 and thereby the function which has been selected for control.

After the function to be controlled has been selected the actual control is accomplished by ganged switches 42 and 43. Each, on closing puts a distinctive modulation on the carrier from transmitter I3, denominated respectively increase signal and decrease signal. In general the extent of control exercised by these signals is proportional to the signals duration. Inasmuch as the two controls are opposed in their effects the switches 42 and 43 are ganged so that both cannot be closed together.

Provision is made in our remote control system for a very necessary safety feature. Certain control signals if inadvertently transmitted to the slave airplane might result in great damage thereandassi:

` position beyond the second step unlesspush but ton 41 also is closed.V In terms of function, switchr 33 following the sending of a Reset signal is operative to transmit the Step signal for oneor two pulses, but in order to transmit a greater number of pulses push button 41 also must be closed.- The operation of switch 34,- by which the function to be selected in the remote selector 28 is indicated in'l control box I I, is similarly restrictedand similarly released.

The means by which these results are accomplished are switches 36 and 31,- double acting relay 46, and three-pole switch 45.

It will be seen that the circuit through the Step terminal of switch 33 passes in parallel paths through switch 45,- the left contact, and push button 41, the left contact, so that when switch 45 is open the Step signal is inoperative unless push button 41 is closed.

The manner in which switch 45 is opened and closed may be traced by reference to Fig.. 6, which is an abstract of the pertinent parts from the circuit of control box I I shown entire inY Fig. 3.

Relay 46 shown in Figs. 3 and 6 is a double` l acting relay under the control of two coils, an-

upper and lower, as shown. Relay 46 operates to open switch 45 when current ilows through its lower coil, but to hold switch 45 closed inthe absence of current inits lower coil and also closed when current flows through both the upper and lower coils. It is seen that the current energizing the Step coil of relay 38 passes through the center contact of switch 45, and so the circuit which moves stepping switches 35, 36, 31 stepwise is inactive so long as switch..45 is4 open unless. switch 41 be closed. And as long as arm 46 of switch 36 is on any of the terminals. H3A-89A current through the lower coil of relay 46 does hold switch 45 open. Throwing switch 34 to Reset restores arm of switch 36 to terminal 86A, current no longer flows through the lower coilof relay 46, and switch again closes. A

The operation when the stepping switches 35, 36and 31 are stepped `to thepositions 2A, 82A, 92A is special. As switch 34` closes for a second pulse the arm 39, 46and 4 I are moved to make contacts with terminals 2A, 82A,` 92A; current then flows through terminal 82Ato the lower coil of relay 46 and also through-terminal` 92A` to the upper coil of relay 45. Relay 46. therefore does not yet open switch 45. However, when switch 34` is opened at the conclusion of the pulse, the upper coilof relay' 46 is deenergized, .and the lower coil,` still ener-` gized, thenpulls the switch open.` Itisnecessary to have a device of this character to delay the cutoi of the transmitted stepping; pulse until along enough pulse can be transmitted to remote receiver 5 to operate the stepping switchesr 51, 59 and 69 in remote selector 28.

Besides the controls exercised by the modulation signals in the circuits connected to terminals B, C, D, E of control box II there are four other controls' carried by modulation signalsgenerated in oscillators connected with terminals F, G, H, I and keyed by the four contacts of switch 44. These are contacts DN, RT, LT and UP. Anyone of them, or any two adjacent, may be closed for the duration desired, the extent of the control exercised being" proportional to the duration of the respective control modulation.

An account of the action of the control in the remote slave plane will now be given, As has been explained the control modulations received move the rudder.

in remote receiver 5 are therein converted Into direct current voltages, each in a separate circuit,

anclone for each' modulation. These separate circuits enter selector 28-Csee Fig. 4)' at the re* spective terminals B-I". for the common ground return of allcircuits. The terminals B"-I are lettered so that the voltages there appearing" are" in response to con-` trol currents set up at the corresponding termi nals Ae-I in control box I I.

A direct voltage pulse appearing at B" passes' through the ResetY coil of relay'1l through safety switch- 14 toAgr'ound and returns through- A. This resets the arms 56., 6I and 62 of Vgan'ge'd stepping switches 51,A 5S and 60 to the positions IGUB, IIGB' and I2DB, respectively,` A voltage' pulse appearing at C passes through-` theV Step coil of relay 1I through-safety switch 14 to ground and return through A". 56', 6I and S2 up one step to terminals I IB, HIB,

I2 IB and each successive pulse moves the switches'v one step further to terminals etc.

Safety switch 14 is ganged to the master switch inthe servo unit 58. Turning this master switch oft blocks all the remote controls on the save airplane without, however, turning off receiver 5,

Awhich it may be desired to keep on so that it will be instantly available for communication or other purposes. The function of safety switch 14 is to prevent ganged switches 51, 59 and. BIJ from being inadvertently changed while the servo unit is out of operation.`

It will be observed that switch 51 selects from several terminals marked To valve section of servo 5B, and several terminals marked Auxiliary functions 12 one channeland connects it to terminal D", similarly one other is selected Afrom the same sets by switch 59 and connected to terminal E".` Thus a control. voltage appearing at D" in response to a control current initiated at D passes through a selected channel and terminal to operate a selected control on the slave plane. For voltage at D" the control is an increasing one, the extent of increase depending on the duration of the control voltage. The channel selected by switch 59 is always for the opposite control to that selected by switch 51. Thus voltage at E" is effective to reverse the control eiected by voltage at D.

Switch 60 is effective only in the position I2 IB to actuate relay 63. In that position current from grounded direct current power supply I3 is passed through the coil of relay 63 moving the armsv of ganged switches 64, 61, 68, 69 to one set of contacts. In all other positions of switch 60 no current passes through the coil of reay 63 and the switch arms are pulled back by spring action to another set of contacts.

The control voltages appearing at terminals F", G and voltage from supply 13 are thus connected at will to either of two groups of channels. These channels are connected at the bank of terminals 19 marked To gyro section of servo." The channels connected with switch 60 in theY I2IB position carry control current to move the ailerons of the plane, the channels connected with switch 60 in the other positions carry current to Control voltage appearing at F is in response to control currentl applied at F and serves to turn the slave plane right. Simi'- larly control voltage applied at G results in turning it left.

Separate control voltages at H" and 1"' are inf A is the teririinalf This moves the arms` assente and control the elevators of the slave plane up and down respectively.

There is thus provided a complete positive remote control from a master station to a slave airplane.

There will now be described an additional feature of the equipment which is valuable. For testing of the remote control system it is desirable to eliminate the modulation and radio link. The circuits are so arranged that this may be done by plugging the terminals A-N of control box ll directly into the corresponding terminals A-N of the selector 28. For use of the equipment in this connection terminal N" has been connected to the ungrounded side of power supply 13. In the test setup current enters control box Il at terminal N from terminal N of selector 28 and serves to furnish the operating voltage for control box Il. In order that this current may appear at the terminals B--I switch 52 is thrown from the Remote position to the Local position. yIhe return circuit is made through the connected grounded terminals A, A. It will be seen that the control currents initiated in control box il now pass directly to selector 28 and form Vthe control voltages to operate in selector 28 in exactly the same manner as when the radio link is interposed.

To illustrate further the number of operating functions possible using this embodiment of the invention, there is set forth herein the following table of operations together with controlling frequencies although the frequencies described are arbitrary values and others can and may be used.

selecting means may be f ed directly to the cor responding ones of said direct current responsive means without the necessity of transmitting and receiving modulated carrier frequency waves.

2. A remote control system comprising a transmitter of a given radio frequency; a plurality of normally inoperative oscillators, each of said oscillators being tuned to a given frequency;

eans connected to said plurality of oscillators for selectively energizing said oscillators; means connected intermediate said transmitter and said plurality of oscillators and responsive to the output of each of said oscillators for frequency modulating said transmitter; a receiver tuned to said radio frequency, including a demodulator; a plurality of channels connected to said demodulator, each of said channels being responsive only to one of said given oscillator frequencies, for producing a. control signal; a plurality of control means connected to control a plurality of operating functions; selecting means connected intermediate said plurality of channels and said plurality of control means for selecting one of said control means in response to a given control signal; and regulating means connected intermediate said plurality of channels and the selected control means for regulating in response to other of said control signals the operation of said selected control means.

3. A system according to claim 2, wherein said means for selectively energizing said oscillators includes a stepping control switch connected to actuate a rst of said oscillators and a reset control switch connected to actuate a second of Step Position Function Freq. OA 1A 2A 3A 4A 5A Increase Brake On... Inc. Pitch... Up Flaps..- Up Gear.

Brake oi Dec.Pitch Down rlaps. Down Gear. Rudder Ruddcr, Rudder Rudder. dom.. do .do do Do.

Elevator.. Elevaton.-. Elevator,... E1evator Elevator. do do do ..do....... Do.

. While the embodiment of the invention described hereinbefore is the preierred one, it will be obvious to those skilled in the art that application of the invention is possible to any type of mobile, stationary reciprocating, or stationary rotating vequipment 4where remote control may be found useful. v

What is claimed is:

. l. A remote control system comprising a transmitter for transmitting a given carrier frequency wave'; means coupled to said transmitter for generating a plurality of modulating frequency Waves; Selecting means connected to said gen-4 erating means, for producing direct current control signals to select given ones of said modulating frequencies to be applied to said transmitter; means connected intermediate said transmitter and said generating means, for modulating said transmitter with said selected modulating irequency waves; a radio receiver tuned to said car'- rier frequency; a first plurality of means in said radio receiver, each of said means being responsive, respectively, to one of said modulating frequencies for producing a direct current control signal; a second plurality of direct current re-` sponsive means, each connected to a corresponding one of said first plurality of means; means for connecting said selecting means directly with said direct current responsive `means so that said direct current control signalsl derived in said said oscillators and wherein said selecting means" comprises a stepping relay connected to be energized by the output of a first of said channels, said first channel being responsive to said first oscillator frequency, a reset relay ,connected to be energized by the output of a second of said channels, said second channel being responsive to`said second oscillator frequency, a plurality of ganged stepping switches, each of said ganged switches having a given reference step, said ganged switches being connected to said stepping relay so that each time said relay is energized each of said ganged switches moves a single step in a given direction, said ganged switches being also connected to said reset relay so that each time said reset relayl is energized each of said ganged switches returns to said reference step.

4. A system according to claim 3 and further including a control box connected to the transmitter having a second stepping relay connected so -as to be energized by saidstepping control switch, a second resetrelay connected so as to be energized by said reset control switch, a plurality of second ganged stepping switches, each of said second ganged switches having a reference step, said second ganged switches being connected to said second stepping relay so that each time said second stepping relay is energized each of said plurality Vof second ganged switches moves a single step in a given direction, saidsecond ganged switches being also connected to said second reset relay so that each time said second reset relay is energized each of said second ganged switches returns to its reference position, and a plurality of indicating light circuits, each connected so as to be energized from a given step of a given one of said second ganged stepping switches.

5. A system according to claim 4 and further including a safety circuit for the means for energizing said oscillators, said safety circuit comprising a safety relay connected to be energized from certain steps of another of said second ganged stepping switches, said safety relay being connected for disabling said rst oscillator so that said rst oscillator cannot be actuated by said stepping control switch, and a normally open switch connected to restore to its original condition said rst oscillator when said switch is actuated.

6. A system according to claim 2 wherein said means for energizing said oscillators includes an increase switch connected to actuate a third oscillator, and a decrease switch connected to actuate a fourth oscillator and wherein said regulating means is connected to respond to the control signals derived from the frequency modulation components of said characteristic radio frequency corresponding to the outputs of said PETER R. MURRAY. DONALD C. BRIGHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,501,684 Oswald July 15, 1924 1,619,228 Williams, Jr., et al. Mar. 1, 1927 1,766,524 Loftin June 24, 1930 1,597,416 Mirick Aug. 24, 1936 2,325,829 Boswau Aug. 3. 1943 2,396,091 vDe Bey Mar. 5, 1946 2,397,088 uClay Mar. 26, 1946 2,397,477 Kellogg Apr. 2, 1946 

